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Smartphone at school

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Romanian Reports in Physics, Vol. 66, No. 4, P. 1236–1252, 2014
University of Bucharest, Faculty of Physics, Bucharest, Romania
Mihai Viteazul School, Călăraşi, Romania
E-mai corresponding author*: [email protected]
Received August 1, 2013
Abstract. Nowadays, smartphones have become an indispensable part of students’ lives.
Used mainly for communication purposes and for entertainment applications, their
educational uses are almost universally ignored by teachers and students alike. The
greatest challenge for a physics teacher is to unlock the great potential of these devices
during the teaching process and shed new light on the diverse and enticing ways in
which students could grasp a better understanding of physics through the simple use of
their pocket-fitting gadgets. Hence, the purpose of this article is to show how
smartphones operating on Android may take physics classes to the next level, as they
can be used both as data collection systems and as data processing systems through
their inbuilt sensors (such as the accelerometer, magnetometer, gyroscope, and the
location and proximity sensor). With the help of open-source applications, these sensors
enable the device to perform a series of measurements, such as the acceleration and
speed of a moving person or vehicle, to establish the user’s location through the method
of trilateration or to measure the angle value of a slope. Therefore, along with the
functions of smartphones themselves, the numerous free applications available on
Google PlayStore are a precious educational resource for a modern physics teacher and
deserve to be explored in a thorough study which will show a new and more
comprehensive way to approach the teaching of physics.
Key words: physics class, smartphone, accelerometer, magnetometer, gyroscope, Android,
open source mobile applications.
Mobile phones have paved their way in the modern world as extremely
flexible, convenient and popular tools designed for communication. Due to their
portability, reduced size and multiple integrated functions, they have become an
almost indispensable accessory for the new generation [1]. But, beyond their
Paper presented at the Annual Scientific Session of Faculty of Physics, University of Bucharest,
June 21, 2013, Bucharest-Magurele, Romania.
Mobile phones in the modern teaching of physics
classical uses, mobile phones hold an enormous, yet insufficiently explored
potential for the education field. As a series of studies point out they can be an
excellent didactic instrument, with state-of-the-art applications in the field of
Physics [2–7]. The cable-based or Bluetooth file transfer, the Internet connectivity
and the audio and video recording functions are just a few of the basic elements
present in classical mobile phones that can be integrated in the didactic process.
Unlike those type of phones, smartphones hold, due to their sensors, a much wider
array of functions and didactically relevant applications.
Having fast processors and large touchscreens, the smartphones have become
mobile working platforms on which students can easily study didactic materials
and process experimental data. At the same time, through a WiFi connection, they
can access a web server or an educational site (a wiki site, for example) on which
these materials are kept or they can study the resources stored on an eLearning
platform designed for their class, such as Moodle.
Most smartphones use the Android operating system, which allows access to
Google Play Store, a digital platform where users can download a large variety of
applications (apps) to use on their mobile phones. The present study offers a
comprehensive picture on the implementation of the free apps which hold a high
educational potential in the Physics classes.
A class of applications of great importance for the study of Physics uses the
phone’s in-built sensors for data acquisition in order to process and interpret it.
This aspect turns the smartphone into an indispensable instrument for the modern
teaching of Physics. As a series of studies [2–7] point out, a portable device so
popular among students can be used to take the didactic process to a whole new
level of expression and enhance the research skills and cognitive abilities of its
a) Experiments using the accelerometer. The measurement instruments
used in Mechanics experiments require precision and versatility. The precision of
angle slope measurements using classical instrumentation is quite low. The mobile
phone offers a methodical alternative for the improvement of such measurements.
In this respect, the application Angle Meter, which is shown in Fig. 1, measures and
displays in real time the angle value of a slope. The periodical recalibration of the
mobile device guarantees a good quality of the measurements.
M. Oprea, Cristina Miron
Fig. 1 – Angle Meter Application. The colored versions may be accessed at
During the lessons “Simple Mechanisms. The Slope”, the smartphone proved
its utility through quick and precise measurements of the slope angles used in
laboratory works such as: determining the friction coefficient on a slope, shown in
Fig. 2, and determining the downward and upward acceleration of objects sliding
on those slopes.
Fig. 2 – Determination of the friction coefficient on a slope using the smartphone. The colored
versions may be accessed at
The tabulation of the angle values measured, as well as calculation of their
tangents, enabled us to determine, through the relationship µ = tgα, the friction
coefficient µ for the following contact surfaces: metal–plastic, rubber–plastic,
wood–plastic and plastic–plastic.
Determining the location and the height of an object can be easily achieved
using an application such as Smart Measure. It uses the phone’s accelerometer to
calculate the tilt angle of the device from the vertical axis and determines with a
high degree of accuracy, based on trigonometric calculations, the distance values to
an object and its height. The principle used for these measurements is rendered in
Fig. 3 and Fig. 4.
Mobile phones in the modern teaching of physics
Fig. 3 – Measurement scheme of the distance smartphone-object.
Fig. 4 – Measurement scheme of the height of the object.
The simple trigonometric relationships
 gz
g z1 = g ⋅ cos θ ⇒ θ = arccos  1
 gz
 ,
M. Oprea, Cristina Miron
tg θ =
tg θ
cos 2 θ
 g z1
 gz
enable the determination of the distance to an object
 gz
 gz
 1
 −1
as well as its real height
H real
 g
=h+H =h+ x  z
 gz
 2
 −1 ,
where h is the phone’s distance from the ground surface.
Fig. 5 – Distance and height measurement on the school premises, using the application Smart
Measure. The colored versions may be accessed at
For example, when measuring the height of a door and the distance from the
door to the observer (Fig. 5a,b), the values obtained with the help of the mobile
phone application were similar to the values obtained with classical measurement
instruments (tape measure). Moreover, with the help of the phone we measured the
projection value gz1=9,47m/s2 of the acceleration of gravity on the vertical axis Oz,
when the device was tilted by an angle θ =15° relative to this axis. Introducing this
value in the calculation formula of the distance x to the object and of the height
Hreal of the object, we obtained values in full accordance with the ones provided by
the application Smart Measure.
The application is very useful during Mechanics lessons to determine the
values of the distance between a reference system and an object, as shown in
Fig. 5c,d, when these values are necessary to calculate the speed of this object and
the time required to walk a certain distance.
Mobile phones in the modern teaching of physics
Another application based on the acceleration sensor is Accelerometer
Monitor, which displays both graphically and numerically in real time (at intervals
of 20 ms), the projection value of the acceleration of gravity on the three axes of
the cartesian coordinate system, as it is shown in Fig. 6.
Fig. 6 – Measurements on the school premises using Accelerometer Monitor. The colored versions
may be accessed at
The values can be optionally recorded in a text file and exported through
Bluetooth, cable data or e-mail on another computer to be processed in MS Excel.
Using this application we determined the value of the acceleration of gravity during
an experiment of free fall of an object from a determined height (h). The selected
object was the mobile phone itself. We suspended it vertically from a nylon thread
along the Oz axis (Fig. 7). Once the application Accelerometer Monitor was
started, the projection values of the acceleration of gravity were displayed on the
three catezian axes Ox, Oy, Oz.
To attenuate the fall of the phone, a soft material (sponge) was placed at the
point of contact with the ground.
Determination of g using the
accelerometer of the smartphone
h – free fall height
Fig. 7 – Determination of g using the accelerometer of the smartphone. The colored versions may be
accessed at
M. Oprea, Cristina Miron
The distance h between the phone and the ground was measured. We
eliminated the suspension thread and the phone moved over the distance h while
the application Accelerometer Monitor was running. After the movement stopped,
the application was turned off and the data recorded by the sensor was saved in a
text file. Its content, which was afterwards visualised with the application Kingsoft
Office installed on the phone, was exported on a laptop in order to be analysed.
Through the MS Excel analysis of the data from the file we built a graphic
containing on the horizontal axis the values of the times when the data was
recorded and on the vertical axis the values of the acceleration of gravity
corresponding to those moments (Fig. 8).
Fig. 8 – Experimental acceleration of gravity values. The colored versions may be accessed at
It can be deduced from this graphic that, until the suspension thread is
eliminated, the acceleration has a value of 9.8m/s2 (with slight variations) on the
Oz axis. After the removal of the thread, during the first tenths of seconds, the
accelerometer records a slight drop in the value of g (transitory recording interval)
and afterwards goes back to the value of 9.8m/s2 which is specific for a free falling
body in the gravitational field of the Earth. This value is maintained until contact
with the ground is made. After impact, the sensor records very high variations of
acceleration due to the dynamic oscillating regime on the damping platform and
stops after a while, going back to the normal value g = 9.8m/s2. The time interval
between the phone’s detachment from the suspension thread and the moment of
ground impact is in fact the falling time t on the distance h, which, according to the
equation of free fall in a gravitational field, allows the calculation of the value of
the acceleration of gravity g:
In our experiment, h = 0.65m, t = 0.36s and the resulting acceleration:
g = 10.03±0,1m/s2.
Mobile phones in the modern teaching of physics
This value is relevant enough considering the experiment has a didactic
purpose. In the graphic (Fig. 8) are indicated quantitative aspects of the experiment
concerning the measurement of the acceleration of gravity, but also important clues
about the temporal intervals of free fall, transitory regime and of the return to the
normal values of g.
For comparative reasons, to validate the results of the accuracy of the
previous experiment, we performed another one, designed to determine the
acceleration of gravity. For this puropose, we used a laser emitter, a system of
mirros, a laser detector (fotoresistor), a plastic ball, a speaker-based acoustic alarm,
a microphone and a laptop with a sound editing software. The block diagram of the
experiment is rendered in the image below (Fig. 9).
Fig. 9 – Experimental scheme. The colored versions may be accessed at
The laser has 10mW power and emits in the red spectrum of the optic domain
(λ = 650 nm). After being reflected on the two mirrors, the laser beam reaches a
photoresistor connected to a sound alarm. When the plastic ball intersects the laser
beams one after another, the emitted sound warning signals are recorded by a
microphone. Afterwards, they are graphically displayed on a laptop which has
sound editing application installed and is connected to the microphone. In Fig. 10
one can see the experimental setup and in Fig. 11 the results obtained with this
M. Oprea, Cristina Miron
Fig. 10 – Experimental setup – Laser-mirrors-detector. The colored versions may be accessed at
Fig. 11 – Recorded audio events. The colored versions may be accessed at
Measuring the distance h between the two laser beams and the time intervals
between the two sound impulses, one can determine, based on the free fall law, the
value of the acceleration of gravity g (Fig. 11).
According to Fig. 9:
v2 = v1 + g ( t2 − t1 ) = v1 + g ⋅ ∆t
v2 = 2 g ( h0 − h2 ) = 2 g ∆h2
v1 = 2 g ( h0 − h1 ) = 2 g ∆h1
v2 − v1 = g ⋅ ∆t
2 g ∆h2 − 2 g ∆h1 = g ⋅ ∆t
Mobile phones in the modern teaching of physics
∆h2 − ∆h1
∆t 2
The experimental values can be found in Table 1.
Table 1
Experimental data using the setup from Fig. 10.
t1 [s]
t2 [s]
∆t [s]
∆t2 [s2]
g [m/s2]
gaverage [m/s2]
The precise measurement of the time interval ∆t associated with the known
time values of the space intervals ∆h2 and ∆h1 have led to a reduced dispersion
(2.33%) of the calculated values of g compared to the known value g = 9,8m/s2.
b. Experiments using the magnetometer. Knowing the local values of the
Earth’s magnetic field represents a priority in geophysics investigations. During the
physics lessons, in order to determine these values, we have used the application
Metal Detector, which is shown in Fig. 12, based on the signals received from the
mobile phone’s magnetic sensor. The average measured level of the Earth’s
magnetic field was around 50µT(50mG). The presence of a ferromagnetic material
determines a strong shift in the value of the local magnetic field of the Earth.
For the practical applications of Magnetism lessons, we have determined and
interpreted the values of the magnetic fields produced by different objects (heaters,
grates, metallic rods, ferrites, magnets of different sizes and compositions, etc.) and
by electromagnetically emissive devices (routers, switches, displays, mobile
phones, high voltage lines, etc.).
Fig. 12 – Magnetic field values near ferromagnetic objects (Metal Detector). The colored versions
may be accessed at
Moreover, we compared the values of the magnetic fields measured in µT
with the application Metal Detector with the values measured in mG with the
application EMF Sensor Free, which is shown in Fig. 13, thus obtaining a very
good match.
M. Oprea, Cristina Miron
Fig. 13 – Magnetic field values measured near electromagnetically emissive sources (EMF Sensor
Free). The colored versions may be accessed at
For the validation of the data obtained with the mobile phone applications,
we set up a classical experiment for the determination of the values of the Earth’s
magnetic field. In this experiment, we used a compass, a coil with N = 100 turns,
an electrical power source with adjustable voltage and a multimeter to measure the
voltage and the intensity of the electrical current (Fig. 16). To establish the exact
N-S direction, we also used two reference compasses. The block diagram of the
experiment can be seen in Fig. 14.
Fig. 14 – Diagram for the determination of the terrestrial magnetic induction.
The CuEm conductor used for the winding had a 0.5mm diameter and was
placed in a multilayer geometry, on a circular bolster with a 30mm radius and 5mm
thickness (Fig. 15).
Mobile phones in the modern teaching of physics
Fig. 15 – The scheme of the coil used in the experiment.
Once the geographical N-S direction is established, the longitudinal axis of
the coil has been placed perpendicular on the direction of the lines of the Earth’s
magnetic field (Fig. 16). Due to a 68 Ω (0.5W) resistor the current through the coil
has been limited to values of tens of mA. The distances from the center of the coil,
on its longitudinal axis, at which the experiments were performed, had the values:
30 mm, 45 mm, 60 mm.
Fig. 16 – Experimental setup (on the left) and axial placement coil – compass (on the right).
The colored versions may be accessed at
We measured deviations of the magnetic needle of the compass due to the
interaction between the Earth’s magnetic field and the magnetic field of the coil on
the interval 0–60° (Fig. 17, Fig. 18).
M. Oprea, Cristina Miron
Fig. 17 – 10° deviation of the magnetic compass needle, voltage 2.00 V, current 20 mA.
The colored versions may be accessed at
Fig. 18 – 30° deviation of the magnetic compass needle, voltage 6.07 V, current 70 mA.
The colored versions may be accessed at
The recorded data enabled the calculation of the magnetic field induction
value on the Oz axis, as shown in Fig. 19:
B ( z) =
N ⋅I
Fig. 19 – The magnetic field produced by a circular coil with N turns on the longitudinal axis Oz.
Mobile phones in the modern teaching of physics
The table containing the measurement data is displayed in Table 2:
Table 2
Experimental data for the determination of the values of the Earth’s magnetic field
z = 30 mm
U [V]
I [mA]
Deviation angle
compass needle
θ [grd]
Bc [µT)
Coil magnetic
Bt [µT]
The Earth’s magnetic field has been deduced from the relation Bt = Bc/tgθ. A
graphic Bc = f (tgθ) was drawn in Fig. 20.
Fig. 20 – The dependence of the magnetic field of the coil on the deviation angle of the compass (θ).
The colored versions may be accessed at
From the slope of this graphic we can determine the value of the terrestrial
magnetic induction Bt. The average value obtained for the terrestrial magnetic
induction (40 µT) is fairly adequate for didactic purposes. Using the magnetometer
from the mobile phone, we measured the average value Bt = 43 µT for the areas
free from magnetic disturbances.
c) Experiments using the GPS sensor. Using the data provided by the
phone’s GPS sensor, the Android Speedometer application offers a large array of
functions neccessary to determine physical measurements of interest for Mechanics
experiments: GPS localizing, N-S geographical orientation, average motion speed,
the maximum speed, the instantaneous speed, the motion time, the distance, as is
shown in Fig. 21.
M. Oprea, Cristina Miron
Fig. 21 – Measurement undertaken with Android Speedometer on a straight walking path.
The colored versions may be accessed at
The didactic efficiency of this application was put to test in an experiment for
the value determination of distance, speed and motion time of an object in an
uniform and rectilinear movement.
During the Mechanics class “The rectilinear and uniform motion”, we tested
the didactic efficiency of this application in an experiment to determine the
distance, speed and motion time. On the sports ground of the school we organized
two groups of students of 5 persons each. In every group, 4 students maintained a
fixed position, while the fifth student went back and forth between two fixed
points. The distance and motion time of each student was measured, using different
measurement instruments. Group 1 used a stop watch and a tape measure, while
Group 2 performed the measurements with the help of the Android Speedometer
application (Fig. 22).
Fig. 22 – Schematic plan of the experiment.
Comparing the final results of the experiment, we noticed an exceptional
efficiency of the method based on the use of the smartphone, reflected in the time
of data acquisition and processing of the measured values, which was considerably
Mobile phones in the modern teaching of physics
This methodology based study has underlined the fact that smartphones have
become didactic instruments neccessary for the modern teaching and learning of
Physics, as some studies on M-Learning concept point out [6, 8, 9, 10, 11]. The
possibility to acquire diverse experimental data through sensors and to process it
using specific application which offer numerical and graphic results relative to the
phenomena being studied, make this device look like a miniature mobile Physics
The smartphones enable a quick access to educational resources situated on
web servers, mobile devices (tablets, other mobile phones) or fixed devices (PCs),
as well as the swift data transfer towards external data storage and processing units.
These capabilities define the mobile phones as digital mobile platform with
important educational uses.
When students feel interested to participate in physics experiments, they try
to get involved actively in learning science concepts. Teachers may use particular
instruments: real experiment [14–15], virtual experiments [16] and Mobile
Learning [17–19]. Smartphones play a key role in the students’ increase of interest
in the study of Physics and the motivation neccessary to study it further.
Smartphones become for them essential tools in class, facilitating a large variety of
calculations and measurements, diminishing the data acquisition and processing
time and contributing to the approach and understanding of a wide spectrum of
physical phenomena.
In conclusion, this study emphasizes an indisputable aspect, on which any
modern didactics of Physics will rely: in the future, the trully smart lessons will be
based on a equally matching device – the smartphone.
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